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United States Patent |
5,052,625
|
Ruskin
|
October 1, 1991
|
Pressure compensating drip irrigation system
Abstract
A drip irrigation system provides drip action of water flowing under
pressure in an irrigation supply conduit. A drip emitter bonded to the
exterior of the supply conduit receives water from the conduit passes the
water through a pressure compensating labyrinthine channel formed
internally in the emitter, and discharges the water from the channel at a
greatly reduced pressure drop so the water drips at a slow drip rate. The
emitter includes an elastomeric pressure compensating diaphragm contained
within the emitter between the exterior of the supply conduit outer wall
and the teeth of the labryinth. When water pressure is applied, the
diaphragm is held in pressure contact with the ends of the teeth to form a
pressure compensating side of the labyrinthine channel, for stabilizing
the output drip rate of the emitter by accommodating flow pressure
variations in the supply conduit. In one embodiment, the emitter is bonded
to the exterior wall of the irrigation supply conduit by magnetic
induction heating techniques. A region of fusible bonding material is
disposed around the outside boundary of the labyrinthine channel, and the
diaphragm is placed inside the emitter over the teeth of the labyrinth and
the emitter is then placed over the supply conduit so the fusible bonding
material overlies the exterior wall of the conduit. The bonding material
is then fused by magnetic induction heating techniques to weld the inside
of the emitter around the periphery of the channel to the exterior wall of
the conduit.
Inventors:
|
Ruskin; Rodney R. (50 Pemberton Pl., San Francisco, CA 94114)
|
Appl. No.:
|
487618 |
Filed:
|
March 2, 1990 |
Current U.S. Class: |
239/542 |
Intern'l Class: |
B05B 015/00 |
Field of Search: |
239/542
|
References Cited
U.S. Patent Documents
3873030 | Mar., 1975 | Barragan.
| |
3979070 | Sep., 1976 | Lemelshtrich.
| |
3998391 | Dec., 1976 | Lemelshtrich | 239/542.
|
4195784 | Apr., 1980 | Gilead.
| |
4209133 | Jun., 1980 | Mehoudar | 239/542.
|
4210287 | Jul., 1980 | Mehoudar.
| |
4307841 | Dec., 1981 | Mehoudar et al. | 239/542.
|
4366926 | Jan., 1983 | Mehoudar | 239/542.
|
4473525 | Sep., 1984 | Drori.
| |
4573640 | Mar., 1986 | Mehoudar | 239/542.
|
Primary Examiner: Kashnikow; Andres
Assistant Examiner: Morris; Lesley
Attorney, Agent or Firm: Christie, Parker & Hale
Claims
What is claimed is:
1. A pressure compensating drip irrigation emitter for connection to the
exterior of a supply conduit, the pressure compensating emitter
comprising:
an upright peripheral outer wall having a peripheral boundary at one end
extending around and leading to an open region within the emitter;
an inside surface exposed to said open region and spaced from the
peripheral boundary of the emitter;
a labyrinthine channel formed in the inside surface of the emitter
comprising spaced apart teeth projecting from said inside surface into the
open region of the emitter;
an elastomeric pressure compensating diaphragm in the open region of the
emitter positioned for contact with the ends of the labyrinth teeth spaced
from said inside surface; and
a bonding material on the peripheral boundary of the upright peripheral
outer wall of the emitter for use in bonding the emitter to the exterior
wall of a supply conduit, to form a sealed chamber inside the emitter in
which the pressure compensating diaphragm is disposed between the exterior
wall of the supply conduit and the labyrinth, so that water flowing in the
supply conduit can pass through an opening in the conduit and into the
sealed chamber and flow to the labyrinth, the water emitted to the sealed
chamber under pressure causing the diaphragm to apply pressure to the
teeth of the labyrinth to seal one side of the labyrinthine channel within
the emitter so that the water emitted to the channel can pass from the
channel to the exterior of the emitter at a pressure compensated slow drip
rate.
2. Apparatus according to claim 1 in which the bonding material is a
fusible material capable of bonding a thermoplastic emitter to a
thermoplastic supply conduit and in which the bonding material is capable
of being bonded to such a thermoplastic pipe by magnetic induction heating
techniques.
3. Apparatus according to claim 1 in which the teeth forming the
labyrinthine channel have their remote ends at the same elevation spaced
from the inside surface of the emitter wall.
4. A drip irrigation system in which at least one drip emitter unit is
bonded to the exterior of a continuous tubular water supply conduit
without severing the conduit to attach the emitter units to the supply
conduit, the system comprising:
an elongated supply conduit for conducting the flow of water under
pressure, the supply conduit having a tubular outer wall of generally
uniform cross sectional configuration continuous with the length of the
conduit;
an emitter bonded to an exterior surface area portion of said continuous
length of conduit, the emitter comprising an upright peripheral outer wall
having a peripheral boundary at one end extending around and leading to an
open region within the emitter; means forming a fused bond between the
peripheral boundary of the emitter outer wall and the supply conduit to
form a sealed chamber inside the emitter, in which a circumferential
surface area portion of the continuous length of conduit forms a base of
the sealed emitter chamber; and a labyrinthine channel formed in the
inside surface of the emitter from spaced apart teeth projecting from the
inside surface into the open region of the emitter; and
an elastomeric pressure compensating diaphragm in the open region of the
sealed emitter chamber and positioned for contact with the ends of the
labyrinth teeth spaced from the inside surface of the emitter, the
pressure compensating diaphragm being disposed within the sealed emitter
chamber between the exterior of the continuous supply conduit and the
labyrinthine channel so that water flowing in the supply conduit flows
through a perforated wall of the supply conduit and into the sealed
chamber to thereby flow to the labyrinth, the water admitted to the sealed
emitter chamber under pressure causing the diaphragm to apply pressure to
the teeth of the labyrinth to seal one side of a labyrinthine channel
within the emitter so that water admitted to the labyrinthine channel can
pass through the channel to the exterior of the emitter at a pressure
compensated slow drip rate.
5. Apparatus according to claim 4 in which the supply pipe and the emitter
are made from thermoplastic materials and the emitter is bonded to the
supply conduit by a fusible bonding material capable of being bonded to
the supply conduit by magnetic induction heating techniques.
6. Apparatus according to claim 4 in which the diaphragm is free to float
between the ends of the teeth and the exterior wall of the supply conduit
when there is no water pressure in the conduit and, when water pressure is
applied to the conduit, the diaphragm is brought into contact with the top
of the teeth to form a sealed labyrinthine channel.
7. A drip irrigation system in which at least one drip emitter unit is
bonded to the exterior of a continuous tubular water supply conduit
without severing the conduit to attach the emitter units to the supply
conduit, the system comprising:
an elongated supply conduit for conducting the flow of water under
pressure, the supply conduit having a tubular outer wall of general
uniform cross sectional configuration continuous with the length of the
conduit;
a drip emitter having an upright peripheral wall bonded to an exterior
surface area portion of said continuous length of supply conduit, the
emitter having an open interior space facing toward said peripheral wall
and having a fused bond between the peripheral wall of the emitter and the
supply conduit for forming a sealed interior chamber inside the emitter,
in which a circumferential surface area portion of the continuous length
of conduit forms a base of the sealed emitter chamber;
a labyrinth formed in an inside surface of the emitter spaced from the
exterior wall of the conduit, the labyrinth being formed by spaced apart
teeth having their ends spaced from the inside surface of the emitter; and
an elastomeric pressure compensating diaphragm within the open interior
space of the sealed emitter chamber for pressure contact with the ends of
the labyrinth teeth so that water admitted under pressure from the supply
conduit through a perforated wall of the supply conduit to the sealed
chamber seals the diaphragm to the ends of the teeth to form a sealed
labyrinthine channel between the diaphragm and the inside surface of the
emitter and so that water admitted to the sealed channel flows through the
channel and is emitted from the channel to the exterior of the emitter at
a slow drip rate controlled by the pressure compensating action of the
diaphragm that accommodates changes in line pressure within the supply
conduit.
8. Apparatus according to claim 7 in which the diaphragm is free to float
between the ends of the teeth and the outer wall of the supply conduit
when there is no water pressure in the conduit and, when water pressure is
applied to the conduit, the diaphragm is brought into contact with the top
of the teeth to form the sealed labyrinthine channel.
9. Apparatus according to claim 7 in which the emitter and the supply
conduit are made from thermoplastic materials and in which the emitter is
bonded to the conduit by a bonding material capable of forming a fusible
bond by magnetic induction heating techniques.
10. A method for manufacturing a pressure compensating drip irrigation
system comprising:
providing an elongated supply conduit for transmitting water under
pressure;
bonding a drip emitter unit to the exterior wall of the supply conduit to
form a sealed interior chamber between the supply conduit and the inside
of the emitter unit, the emitter comprising an upright wall having an
inside surface facing an interior of the emitter and in which the upright
wall has a peripheral boundary for engagement with the supply conduit, the
emitter further including a labyrinth formed in the inside surface of the
emitter, the labyrinth being formed by spaced apart teeth having their
ends spaced from the inside surface of the emitter;
placing an elastomeric diaphragm in the inside region of the emitter,
adjacent the ends of the labyrinth teeth; and
bonding the peripheral boundary of the emitter to the exterior wall of the
supply conduit to form a sealed chamber within the emitter on the exterior
side of the supply conduit in which the diaphragm is positioned inside the
emitter in a space between the exterior wall of the conduit and the
labyrinth, the elastomeric pressure compensating diaphragm being arranged
for pressure contact with the ends of the labyrinth teeth so that water
admitted under pressure from the supply conduit to the sealed chamber
seals the diaphragm to the teeth of the labyrinth to form a sealed
labyrinthine channel between the diaphragm and the inside surface of the
emitter, and so that water admitted to the sealed channel flows through
the channel and is emitted from the channel at a slow drip rate controlled
by pressure compensating action of the elastomeric diaphragm that
accommodates changes in line pressure within the supply conduit.
11. The method according to claim 10 including:
the steps of placing the inside surface of the emitter adjacent the
exterior wall of the supply conduit, providing a region of a fusible
bonding material around the peripheral boundary of the emitter and in
contact with the exterior wall of the supply pipe, the bonding material
being capable of forming a bond between the supply conduit and the emitter
by magnetic induction heating techniques; and
fusing the bonding material by heat induced by a magnetic induction heating
generator to bond the emitter to the exterior wall of the supply pipe to
form a closed, internal fluid pressure reducing chamber between the
emitter and the exterior wall of the supply pipe.
12. The method according to claim 10 in which the bonding material is a
ferromagnetic, electrically conductive material.
13. The method according to claim 10 in which the emitter peripheral
boundary includes a recess extending around the periphery of the emitter
and the bonding material is positioned between the supply conduit and the
emitter within the recess in the peripheral wall of the emitter, and
including subjecting the bonding material to the magnetic induction
heating to fuse by heat the bonding material while the recess confines the
fused bonding material so that the fused bonding material forms a seal
between portions of the emitter and the supply conduit extending around
the outside of the chamber boundary to seal the chamber boundary.
14. Apparatus according to claim 4, in which the emitter is a one piece
unit made from a thermoplastic material and the supply conduit is made of
a flexible thermoplastic material of substantially circular cross section
free of surface irregularities along said continuous length of conduit.
15. Apparatus according to claim 4, in which a plurality of said emitters
are bonded to the supply conduit at spaced apart intervals along said
continuous length of conduit.
16. Apparatus according to claim 4, in which the water enters the emitter
through said perforated supply conduit wall free from any intrusion of the
emitter into the interior of the supply conduit.
17. Apparatus according to claim 7, in which the emitter is a one piece
unit made from a thermoplastic material and the supply conduit is made of
a flexible thermoplastic material of substantially circular cross section
free of surface irregularities along said continuous length of conduit.
18. Apparatus according to claim 7, in which a plurality of said emitters
are bonded to the supply conduit at spaced apart intervals along said
continuous lengths of conduit.
19. Apparatus according to claim 7, in which the water enters the emitter
through said perforated supply conduit wall free from any intrusion of the
emitter into the interior of the supply conduit.
20. A drip irrigation system comprising:
a supply conduit for conducting the flow of water under pressure;
an emitter bonded to an outer wall of the supply conduit, the emitter
comprising an upright peripheral outer wall having a peripheral boundary
of one end extending around and leading to an open region within the
emitter, an inside surface exposed to said open region and spaced from the
peripheral boundary of the emitter, the peripheral boundary of the upright
peripheral wall being bonded to the supply conduit to form a sealed
chamber inside the emitter in which the supply pipe and the emitter are
made from thermoplastic materials and the emitter is bonded to the supply
pipe by a bonding material for forming a bond to the supply conduit by
magnetic induction heating techniques;
a labyrinthine channel formed in the inside surface of the emitter from
spaced apart teeth projecting from the inside surface into the open region
of the emitter; and
an elastomeric pressure compensating diaphragm in the open region of the
emitter positioned for contact with the ends of the labyrinth teeth spaced
from the inside surface of the emitter, the pressure compensating
diaphragm being disposed within the sealed emitter chamber between the
exterior wall of the supply conduit and the labyrinthine channel so that
water flowing in the conduit and into the sealed chamber can flow to the
labyrinth, the water admitted to the sealed chamber under pressure causing
the diaphragm to apply pressure to the teeth of the labyrinth to seal one
side of the labyrinthine channel within the emitter so that water admitted
to the labyrinthine channel can pass through the channel to the exterior
of the emitter at a pressure compensated slow drip rate.
21. A drip irrigation system comprising:
a supply conduit:
a drip emitter having an upright wall secured to the exterior wall of the
supply conduit for forming a sealed interior chamber between the supply
conduit and the inside of the upright wall, in which the emitter and the
supply conduit are made from thermoplastic materials and in which the
emitter is bonded to the conduit by a bonding material for forming a
fusible bond by magnetic induction heating techniques;
a labyrinth formed in an inside surface of the emitter spaced from the
exterior wall of the conduit, the labyrinth being formed by spaced apart
teeth having their ends spaced from the inside surface of the emitter;
an elastomeric pressure compensating diaphragm within the sealed chamber
for pressure contact with the ends of the labyrinth teeth, so that water
admitted under pressure from the supply conduit to the sealed chamber
seals the diaphragm to the ends of the teeth of the labyrinth to form a
sealed labyrinthine channel between the diaphragm and the inside surface
of the emitter and so that water admitted to the sealed channel flows
through the channel and is emitted from the channel to the exterior of the
emitter at a slow drip rate controlled by the pressure compensating action
of the diaphragm that accommodates changes in line pressure within the
supply conduit.
Description
FIELD OF THE INVENTION
This invention relates generally to drip irrigation, and more particularly,
to a pressure compensating drip irrigation system.
BACKGROUND OF THE INVENTION
Drip irrigation systems usually include a continuous irrigation water
supply line with separate emitter units installed on the line, or in the
line, usually at regular intervals. Irrigation water flows through the
supply line under pressure, and a small amount of water continuously drips
out at the intervals where the drip emitter units are installed. Drip
irrigation has proved highly successful in producing greater growth of
vegetation for the same amount of water when compared with conventional
irrigation techniques.
There is a continuing need for a low cost dripper system having reliable
performance in terms of uniform flow rates and resistance to clogging at
normal operating pressures of say between 10 to 15 psi. (The dripper of
this invention operates in a range from 10 to 50 psi.) A single hole in
the water supply line may be the cheapest of drip systems, but such an
approach is not satisfactory in most cases. The hole in the pipe wall must
be of minute size to produce the desired drip rate. However, the required
hole size is so small that blockage is almost inevitable at a number of
places along the line, even with filtering. Moreover, a minute hole limits
the operating pressure in the supply line to a maximum of about 5 psi. At
a higher, more desirable line pressure of at least 15 psi, the water jets
or sprays through the holes in the pipe wall. By reliably running a drip
irrigation system at the higher operating pressure, longer dripper lines
can be used; more output, in terms of gallons of water per hour, is
produced; and the system can work on undulating ground (up and down
slopes) as well as on flat ground.
A large number of more sophisticated drip irrigation systems have been
developed for the purpose of overcoming the problems inherent in a single
hole in the wall of the irrigation line. A common and successful approach
involves use of separate emitter units installed in or on the supply line.
The emitter unit taps off a portion of the water flowing in the supply
line and passes the water through a labyrinth or other circuitous path
that produces a large pressure drop in the water and discharges it at a
uniform drip rate. Generally, such pressure-reducing labyrinthine emitter
units are successful because they can use a large enough hole in the
supply pipe and a wide enough passage through the labyrinth to avoid
clogging in most cases, and they can be used at higher line pressures.
There is a need for a drip irrigation emitter that is simple in structure
so that manufacturing costs are low, while also having the capability of
being assembled with reasonably low capital and labor costs. It is also
desirable that the emitter be capable of use within thin-wall pipe as well
as more permanent heavy-wall pipe. Orchards and vineyards, for example,
commonly use permanent drip irrigation systems, whereas cheaper thin-wall
pipe can be used for temporary drip irrigation sites. A low cost drip
irrigation system can be particularly important because of its use in
temporary irrigation sites where irrigation systems of the lowest possible
cost are needed. For example, inexpensive temporary irrigation systems can
be used because of harvesting techniques where crops such as cane sugar
are harvested by bulldozing the entire field, including the above-surface
portion of the irrigation system. Temporary irrigation systems also are
used on temporary growing sites for row crops such as lettuce, tomatoes,
strawberries, cotton, and flowers, for example.
The drip irrigation systems presently known are not entirely satisfactory
in terms of low cost, reliability and uniform drip rates, non-interference
with free flow in the dripper line, resistance to clogging, and capability
of use with thin-wall pipe as well as more permanent heavy-wall pipes. One
presently known drip irrigation unit is an insert-type system in which a
portion of the drip irrigation unit is inserted into one end of an
irrigation supply line. The end of another irrigation line is passed over
the remainder of the drip irrigation unit. Flow is between the exterior
labyrinth surface of the inserted unit and the interior of the irrigation
pipe wall. The fit is a cold friction fit which can introduce serious
quality control problems, since the annular spaces can be subject to
considerable variation because of lack of uniformity commonly present in
the pipe inner diameter. This unit must be used with heavy-wall pipe
because internal flow pressures can cause a thin-wall pipe to expand
outwardly just enough to allow the water passing through the labyrinth to
skip over teeth in the labyrinth and short circuit a portion of the
labyrinth which, in turn, can produce an undesired change in drip rate at
the end of the labyrinth. The pipe is cut to insert the dripper. This
creates a risk of separation in the field.
Another insert-type drip irrigation unit is a complex pressure-compensated
unit in which the labyrinth for providing the pressure drop is bonded to
the interior wall of the irrigation pipe by bonding legs. Pressure
compensation is provided by a rubber diaphragm which is pressed into and
blocks part of the labyrinth as pressure is increased within the pipe.
This arrangement requires expensive equipment to insert the drippers
during extrusion of the pipe.
Another insert-type drip irrigation unit is assembled during extrusion of
the plastic irrigation pipe. The unit is made by heating the plastic pipe
(from the heat of extrusion). The dripper emitter unit is then inserted
into the desired position within the pipe. Heat from the molten pipe bonds
the interior of the pipe to the exterior of the inserted dripper unit.
Such extrusion equipment is expensive, in part, because it requires
precise temperature control during assembly. That is, good adhesion must
be provided between the pipe and the emitter to ensure that the dripper
will function properly hydraulically. If the temperature is too high, the
softened pipe wall can flow into portions of the passageway through the
labyrinth. If the temperature is too low, the adhesion is poor. Inasmuch
as this arrangement uses the inner wall of the supply pipe to form the
outer wall of the flow passage through the dripper, the pressure inside
the dripper can open the bond between the inside wall of the pipe and the
outside surface of the dripper.
A limitation of such insert-type units is hydraulic interference with flow
through the interior of the irrigation pipe. As a result, the possible
free flow through the irrigation pipe is reduced which, in use, reduces
the useful length of the dripper line. The pipe is either cut to allow
insertion of the dripper after extrusion of the pipe, which creates the
risk of separation in the field, or else expensive equipment is required
to allow insertion of the dripper into the pipe during the extrusion
process. Insertion of drippers after the extrusion process also can cause
stress cracks in the polyethylene pipe.
Another drip irrigation system is a so-called clip-on bayonet system, in
which a bayonet or barb on the emitter is passed through the wall of an
irrigation pipe and so the emitter unit itself is mounted on the exterior
of the supply pipe. Water is drawn through the bayonet into a labyrinth
formed in the interior of the exterior dripper unit. The dripper unit is
usually a high-profile unit which can cause hooking and entangling with
weeds, grass, etc. when pulled around a field when laying the irrigation
unit. All known bayonet systems are complex multi-component systems which
are relatively expensive to manufacture and assemble because of material
and manual assembly costs. Bayonet systems typically require a heavy-wall
pipe to properly hold the bayonet in place, and the inserted bayonet
interferes with the free flow through the irrigation line.
The present invention provides an irrigation system with a single-component
drip emitter unit that can be constructed at a much lower cost, while
overcoming disadvantages of the prior drip irrigation units described
above.
In recent years there have been a number of drip irrigation systems in
which the emitter includes a resiliently flexible membrane formed of a
natural or synthetic elastomeric material. The flexible membrane is
displaceable toward or away from the flow-restricting flow path in the
dripper in response to flow pressure variations in the conduit so as to
stabilize the drip rate of the emitter with respect to variations in line
pressure. There are several pressure compensating drippers which are
separate units and which are attached to the supply conduit by a barb, for
example, the pressure compensation dripper shown in Mehoudar (U.S. Pat.
No. 4,209,133). This is a complicated, four-part emitter which is both
expensive to manufacture and expensive to install in the field. At the
present time, it costs about U.S. $0.05 per emitter for labor to install
such an emitter in the field. Furthermore, since farmers frequently wish
to pull the dripper line out of the field, an emitter such as the '133
emitter will catch on stalks and pull off the line. To solve these
problems, a dripper such as that shown in Mehoudar U.S. Pat. No. 4,210,287
was developed in which the emitter is inside the supply conduit. However,
this is still an expensive solution to the problem because precautions
must be taken to prevent the rubber diaphragm from being drawn out of the
emitter by the vacuum which can result from water draining out of the
system. This entails assembling the dripper out of several parts before
inserting it into the supply tube. The machinery to insert parts into the
center of the supply tube during extrusion is very expensive. Finally, the
thicker wall section of the tube itself demonstrates the difficulty in
producing consistent adhesion by means of the heat of the extruded
material alone. This thicker wall section also increases material costs.
The present invention provides a pressure compensating emitter for a drip
irrigation system which solves the problems described above. The dripper
itself is a simple molded article made by using a two-material molding
technique which is inexpensive in both material and labor costs. The
result is a low cost dripper which is not only pressure compensating, but
which also can be pulled out of the field and used again without the risk
of losing emitters on the irrigation supply line. The emitter of the
present invention also does not have barbs or other parts disturbing the
water flow through the tube which results in less pressure loss and a
saving of power costs. Other advantages also are provided.
SUMMARY OF THE INVENTION
Briefly, one embodiment of the invention comprises a drip irrigation system
which includes a supply conduit and a drip emitter having an upright wall
secured to the exterior wall of the supply conduit and forming a sealed
interior chamber between the supply conduit and the inside of the upright
wall. A labyrinth formed in the inside surface of the emitter spaced from
the exterior wall of the conduit is formed by spaced apart labyrinth teeth
having their ends spaced from the inside surface of the emitter. An
elastomeric pressure compensating diaphragm is disposed within the sealed
chamber for pressure contact with the ends of the labyrinth teeth so that
water admitted under pressure from the supply conduit to the sealed
chamber seals the diaphragm to the teeth of the labyrinth. This forms a
sealed labyrinthine channel between the diaphragm and the inside surface
of the emitter. Water admitted to the sealed chamber flows through the
sealed labyrinthine channel and is emitted from the channel at a slow drip
rate controlled by the pressure compensating action of the diaphragm that
accommodates changes in line pressure within the supply conduit.
The present invention provides significant improvements in drip irrigation.
By placing the elastomeric diaphragm between the outside wall of the
supply tube and the top of the labyrinth teeth, the diaphragm seals to the
tops of the labyrinth teeth in a continuous, fluid-tight seal that can
accommodate slight differences in the thickness of the teeth. The
diaphragm thus provides pressure compensation and simultaneously acts as a
hydraulic seal of the dripper mounted to the outside wall of the supply
tube. This invention also allows the dripper to be reduced in length
substantially, thereby saving material and molding costs. The elastomeric
diaphragm is free to float between the top of the labyrinth teeth and the
outside of the supply tube when there is no water pressure in the system.
When the water pressure is applied, the diaphragm is brought into contact
with the top of the teeth, and any impurities which may have been caught
in the dripper during the previous irrigation cycle are expelled.
As a further advantage, the dripper can be formed as a bond-on dripper in
which the peripheral boundary of the emitter unit can be easily bonded to
the exterior wall of the supply conduit using a ferromagnetic bonding
material at the boundary responsive to magnetic induction heating
techniques. These techniques combined with the arrangement of the
elastomeric diaphragm inside the bondon emitter greatly simplify assembly
and reduce costs.
Because the diaphragm is enclosed by the dripper body and the outside wall
of the supply tube, it cannot be disturbed by the flow of water through
the tube as happens with a dripper inserted inside the supply tube, such
as the Mehoudar '287 device described above. Hence, the outside wall of
the tube acts as the diaphragm retaining wall at no cost compared with
prior art systems which require more expensive and complicated systems for
retaining the pressure compensating diaphragm within the emitter.
These and other aspects of the invention will be more fully understood by
referring to the following detailed description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view illustrating a pressure compensating drip
irrigation emitter bonded to the exterior of an irrigation supply conduit.
FIG. 2 is an elevation view showing the inside region of the emitter.
FIG. 3 a schematic illustration of the dimensions of a labyrinthine drip
irrigation channel contained in the emitter.
FIG. 4 is a longitudinal cross-sectional illustration of a pressure
compensating emitter.
FIG. 5 is a cross-sectional view taken on line 5--5 of FIG. 4.
FIG. 6 is a fragmentary cross-sectional view illustrating a means for
retaining a pressure compensating diaphragm.
FIG. 7 is a fragmentary cross-sectional view illustrating an inlet region
of the pressure compensating emitter.
FIG. 8 is a fragmentary cross-sectional view taken on line 8--8 of FIG. 1
and illustrating the pressure compensating emitter bonded to the exterior
wall of the irrigation supply conduit.
DETAILED DESCRIPTION
FIG. 1 is a perspective view showing a drip irrigation emitter unit 10
secured to the exterior wall of a conventional tubular irrigation supply
conduit 12 of circular cross-section. The supply pipe is conventional in
the sense that it has a smooth interior and exterior surface, i.e., no
surface irregularities need to be formed in the inside or outside wall of
the supply pipe to conform to use with the emitter unit 10. In one
embodiment, the supply conduit 12 is made from a somewhat flexible,
thin-walled plastic material, e.g., a thermoplastic material such as
polyethylene. The drip unit also can be made from a thermoplastic material
such as polyethylene. In one embodiment, the emitter unit is made from the
same material as the supply conduit, in part to provide good adhesion
between the emitter and the conduit. The emitter unit can be made from a
flexible plastic material and adhered to a flexible, thin-walled plastic
pipe by bonding techniques described below.
Only one emitter unit is shown in the drawing for simplicity. In practice,
a drip irrigation system can be formed by securing a number of the drip
emitter units to a continuous irrigation supply pipeline at intervals
along the length of the pipeline. Each emitter unit taps off a portion of
the water flowing through the pipeline and discharges the water from the
emitter at a slow drip rate.
The emitter is preferably a one-piece unit, injection molded in a complex
shape which is elongated and generally rectangular in its outer profile
when the emitter is viewed from above or from inside as in FIG. 2. When
viewed in cross-section as in FIGS. 5 or 8, the emitter has a generally
inverted U-shaped lower portion forming narrow, concavely curved, marginal
flanges 14 and 16 extending longitudinally and parallel to one another
along opposite sides of the emitter. A long, central region 18 of the
emitter projects upwardly between the side flanges 14 and 16. The long,
central region forms an elongated, rectangular, raised section which is
inverted U-shaped in cross-section and of uniform width along the main
axis of the emitter from one end to the other. The long, central region of
the emitter has a rounded, inverted U-shaped, upper surface 19 spaced from
the bottom of the emitter. The flanges 14 and 16 form the bottom of the
emitter along its opposite sides. The inverted U-shaped, front and rear
bottom peripheral surfaces 20 and 22 of the emitter extend parallel to one
another between the side flanges along the front and rear ends of the
emitter.
A narrow, rectangular recess 24 extends around the periphery of the emitter
inside surface. Parallel opposite sides of the rectangular recess are
formed in the curved inside faces of the side flanges 14 and 16. Parallel
opposite ends of the rectangular recess are formed at right angles to the
long sides of the rectangle and are inverted U-shaped in cross-section in
the inside faces of the end surfaces 20 and 22 of the emitter. Thus, when
the emitter is viewed from the inside as in FIG. 2, the narrow,
rectangular recess 24 is formed between a rectangular outer wall 26 on the
outside wall of the emitter and a rectangular inside wall 28 spaced
uniformly inside the outer wall. The rectangular remote ends of the outer
and inner walls of the recess are shaped and formed so as to essentially
match the curved outer surface contour of the supply conduit 12, so that
the bottom peripheral portion of the emitter can lie essentially in flat
contact with the supply conduit outer wall when the emitter is bonded to
the outer wall as described below. The rectangular outer recess provides a
means for containing a fusible bonding material 29, described below, for
extending continuously around the rectangular bottom periphery of the
emitter.
The emitter body also includes one or more fluid discharge ports 30
extending through an exterior discharge region 32 near one end of the
emitter. The discharge region 32 is molded to the main body 18 of the
emitter and projects away from the main central section of the emitter to
provide a means for discharging water from the interior of the emitter to
the exterior of the emitter at a slow drip rate.
Referring to FIGS. 4, 5 and 8, a longitudinally extending, rectangular,
downwardly opening cavity 34 extends axially along the inside of the
emitter. The cavity is rectangular when viewed in plan view as in FIG. 2.
The cavity has long, parallel, upright side walls 36 and 38 extending
parallel to the sides of the emitter, and short, parallel, upright end
walls 40 and 42 at right angles to the side walls of the cavity. The long
side walls of the cavity are spaced inwardly and parallel to the
longitudinal walls of the inside wall 28 of the rectangular recess 24, and
the short end walls of the cavity are spaced inwardly from and parallel to
the lateral end walls forming the inside end wall portion of the
rectangular recess. The cavity has a flat bottom wall 44 which faces
downwardly toward the open bottom side of the emitter. The plane of the
flat bottom wall is at right angles to the upright side walls of the
rectangular cavity.
A labyrinthine channel 46 is formed as a recess in the flat, bottom surface
44 of the emitter interior. The labyrinthine channel is formed by a
plurality of longitudinally spaced apart, elongated ribs or teeth 48
projecting into the channel from both sides of the channel. The teeth are
interleaved along the length of the channel, are generally parallel to one
another, generally perpendicular to the axis of the channel, are of
uniform size and shape, and are equidistantly spaced apart along the
channel. The alternating teeth therefore form a labyrinthine channel that
continuously reverses direction from an inlet end 50 (which opens through
the end wall 40) to the discharge end of the channel and its discharge
port 30. The arrows in FIG. 2 best illustrate the continuous reversal of
direction of water passing through the labyrinth formed by the channel. As
illustrated best in FIGS. 4, 5, 7 and 8, the tops of the teeth 48 (which
are the remote end of the teeth spaced below the bottom surface 52 of the
channel) are at the same flat elevation as the flat bottom surface 44 of
the chamber 34.
A narrow, circular well 54 is formed at the discharge end of the channel so
that water passing through the channel can pass into the circular well.
The well is continuous with the level of the channel bottom. A circular,
projecting region 56 in the center of the well has a flat bottom formed
spaced below the flat bottom surface 44 of the interior chamber. A narrow
slot 58 passes axially through the projecting center of the well for
providing a narrow channel between the end of the labyrinthine channel and
the discharge port 30 which passes through the center of the circular,
projecting region 56 inside the well.
Referring to FIGS. 2, 3 and 7, an example of the dimensions of one
embodiment of the invention is as follows, the following dimensions being
in millimeters: a=8.0, b=1.0, c=0.5, d=0.2, e=1.3, f=2.4, g=0.38, h=1.3,
i=3.5, j=5.0, k=1.0 and l=0.3.
Referring to FIGS. 4 through 8, a thin, rectangular, elastomeric pressure
compensating diaphragm 60 is disposed within the hollow interior region of
the emitter for contacting the bottom edges of the labyrinth teeth. The
pressure compensating diaphragm is preferably made from a rubber material
such as EPDM rubber of a 40 Shore A hardness. The diaphragm is configured
and arranged to seal to the bottoms of the labyrinth teeth to provide a
hydraulic seal for one side of the labyrinthine channel spaced remote from
the bottom 52 of the channel. The length of the diaphragm extends from the
end wall 40 to the opposite end wall 42 as shown in FIG. 2, and the width
of the diaphragm spans the distance between the side walls 36 and 38. In
the example described above, the dimensions of the diaphragm are 7.9 mm in
width, 15.9 mm in length and 1.0 mm thick. As shown best in FIG. 6, the
side walls 36 and 38 of the hollow, internal chamber can have narrow bumps
62 projecting outwardly over the diaphragm to retain the diaphragm in the
interior space adjacent the bottoms of the labyrinth teeth 48. The end of
the diaphragm remote from the discharge end of the emitter contacts the
front edge 40 of the internal chamber so that an end of the diaphragm
shown in phantom lines at 64 is spaced inwardly from an end wall 66 of the
chamber to provide a narrow inlet opening at 50.
A variety of methods can be used for securing the emitter to the exterior
side wall of the supply pipe. For example, such plastic welding techniques
as heat welding, spin welding, adhesive bonding, high frequency bonding,
ultrasonic bonding, electromagnetic bonding, hot air welding and the like
can be used. However, best results for the thermoplastic materials used
are provided when magnetic induction heat bonding techniques are used. In
accordance with these bonding techniques, the rectangular recess 24 which
extends around the lower periphery of the emitter is filled with the
bonding material 29 which can be of any various materials capable of
forming a reliable bond. In the preferred embodiment, the bonding material
is a fusible material that is fused to a molten condition in which it
creates a bond that welds or otherwise seals the lower peripheral portion
of the emitter to the exterior side wall of the supply conduit. In the
illustrated embodiment using magnetic induction bonding techniques, the
bonding material is a thermoplastic material filled with ferromagnetic
particles, and in the presently preferred embodiment, the bonding material
is a high density polyethylene filled with iron powder. The narrow
rectangular recess 24 is preferably filled with a block of the bonding
material which projects away from the bottom of the emitter which forms
the rectangular side boundaries for the recess, and the emitter is then
welded to a smooth, continuous section of the exterior side wall of the
pipe by electromagnetic induction heating techniques. In accordance with
such techniques, heat is generated in the bonding material by a variable
magnetic field induced by a magnetic coil of a high frequency induction
heating generator. The bonding material is an electromagnetic energy
absorbing material, both magnetizable and electrically conductive. Heat is
rapidly generated when the bonding material is exposed to the magnetic
field and this heat is readily transferred to abutting thermoplastic
surfaces of the emitter and the supply pipe, rapidly raising their
temperatures to just in excess of their melting points, creating a heat
bonded joint between the periphery of the emitter and the supply pipe
through the molten bonding material. The bond thus formed is a water-tight
seal formed around the entire outer boundary of the emitter.
Thus, the interior chamber is closed within the emitter and the interior
space within the emitter is formed between the outside wall of the conduit
and the walls of the emitter chamber formed internally in the emitter
body. A hole (not shown) is formed in the side wall of the supply conduit
so that water passing through the hole then passes through the inlet
opening 50 of the sealed emitter chamber and into the labyrinthine
passage. The position of this hole is not required to be precise as long
as it is under the rather large cavity 34. This is not the case for the
dripper shown in Mehoudar U.S. Pat. No. 4,210,287 where positioning of the
hole from outside the opaque conduit to meet the small exit chamber
located inside the conduit is a more difficult procedure.
In using the drip irrigation unit, water under pressure of say 10-15 psi
flows in the irrigation supply pipe. A small amount of the water in the
supply pipe passes through the hole in the wall of the supply pipe and
into the labyrinthine chamber which creates an appreciable pressure drop
along the path of the water as it flows from the inlet end 50 toward the
discharge end of the labyrinth where the water is discharged through the
discharge opening 30 at a slow drip rate. During use, the pressure
compensating diaphragm forms one side of the sealed, labyrinthine pressure
reducing chamber between the supply pipe and the tops of the labyrinth
teeth. The flexibility of the rubber diaphragm provides pressure
compensation to uniformly smooth out variations in system pressure. The
diaphragm is free to float between the top of the teeth and the outside of
the tube when there is no water pressure in the system, but when water
pressure is applied, the diaphragm is brought into contact with the tops
of the teeth to seal to the tops of teeth to produce the necessary
pressure drop. As one advantage, any impurities which may have been caught
in the dripper during the previous irrigation cycle are expelled by
movement of the rubber diaphragm when water pressure is applied.
The present invention is believed to provide a substantial advance in the
art in that the rubber diaphragm not only acts as a pressure compensating
device, but also simultaneously acts as the hydraulic seal of the dripper
mounted to the outside wall of the tube. Because the rubber diaphragm is
enclosed by the dripper body and the outside wall of the supply tube, it
cannot be disturbed by the flow of water through the tube, as happens with
a dripper inserted inside the supply tube as shown in Mehoudar '287
described previously. Thus, the outside wall of the tube acts as the
diaphragm retaining wall and, as a result, the dripper can be made at an
extremely low cost with high quality. The dripper is easier to manufacture
and quality control with substantially lower capital costs than in the
case of a dripper inserted into the interior of the supply tube. The
dripper of this invention also can be made with no undercuts and can be
molded without sides or core-pin pullers.
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